Multiple fuel system for internal combustion engines

ABSTRACT

A fuel management system mounted on a vehicle is operative to feed individually or a mixture of grades of relatively low, intermediate, and high autoignition temperature fuels to an associated internal combustion engine. The system includes an on board separation unit (OBS unit) for receiving and separating intermediate autoignition temperature (IAT) fuel into low and high autoignition temperature fuels, LAT and HAT, respectively. The production rate of the LAT and HAT fuels by the OBS unit is controlled to substantially match the consumption requirements of the engine at any given time for the LAT and HAT fuels.

This application claims the benefit of U.S. Provisional Application No.61/009,266 filed Dec. 27, 2007.

RELATED APPLICATIONS

The present invention is related to U.S. Provisional Application No.61/009,336, entitled “Fuel Management For Vehicles Equipped WithMultiple Tanks for Different Grades Of Fuel,” filed on the same dayherewith, having common inventorship herewith, and common ownership; toSer. No. 11/187,672, filed on Jul. 22, 2005, for “Heat Pipe For SelfLimiting Heating Of Gasoline For Onboard Octane Segregation”; and toProvisional Application No. 60/785,426, filed on Mar. 24, 2006, for“Heat Pipe With Controlled Fluid Charge.” The teachings of the relatedApplications are incorporated by reference herein to the extent thatthey do not conflict herewith.

FIELD OF THE INVENTION

The present invention relates generally to systems for using multiplefuel of differing grades, such as different research octane numbers(RON) for spark ignition engines, and different cetane numbers forcompression ignition engines, either individually or in a predeterminedmixture for operating an internal combustion engine.

BACKGROUND OF THE INVENTION

Both petroleum refineries and engine manufacturers are constantly facedwith the challenge of continually improving their products to meetincreasingly severe governmental efficiency and emission requirements,and consumers' desires for enhanced performance. For example, inproducing a fuel suitable for use in an internal combustion engine,petroleum producers blend a plurality of hydrocarbon containing streamsto produce a product that will meet governmental combustion emissionregulations and the engine manufacturers performance fuel criteria, suchas research octane number (RON). Similarly, engine manufacturersconventionally design spark ignition type internal combustion enginesaround the properties of the fuel. For example, engine manufacturersendeavor to inhibit to the maximum extent possible the phenomenon ofauto-ignition which typically results in knocking, and can cause enginedamage, when a fuel with insufficient knock-resistance is combusted inthe engine.

Under typical driving situations, engines operate under a wide range ofconditions depending on many factors including ambient conditions (airtemperature, humidity, etc.), vehicle load, speed, gear ratio, rate ofacceleration, and the like. Engine manufacturers and fuel blenders haveto design products which perform well under virtually all such diverseconditions. This requires compromise, as often times fuel properties orengine parameters that are desirable under certain speed/load conditionsprove detrimental to overall performance at other speed/load conditions.Conventionally, vehicular fuels are supplied in two or three grades,typically distinguished by their Research Octane Number, or RON.Generally, the selection of fuel grade is based upon the enginespecifications. However, once the fuel is “onboard,” it becomes a “onefuel fits all” and must be designed to accommodate diverse speed, loadand other driving conditions.

Attempts have been made to overcome the limitations of providing only asingle grade of fuel for driving an internal combustion engine. In suchattempts, systems have been developed for providing multiple fuels ofdifferent RON numbers “onboard” a vehicle, for driving the associatedinternal combustion engine with individual ones or mixtures of the fuelsin a controlled manner for meeting the engine's drive cycle conditionsover a broad range of operating conditions of the engine. Although theseprior systems do offer an enhanced performance of an internal combustionengine, it is clear to those of skill in the art that such systemsrequire further improvement.

SUMMARY OF THE INVENTION

An object of present invention is to provide for both production andconsumption control of a plurality of fuels having differing RON numbersfor optimizing the operation of an internal combustion engine.

Another object of the present invention is to provide an improvedmultiple RON fuel supply system that includes an onboard separation(OBS) apparatus for separating intermediate research octane (IRON) fuelfrom a main tank into at least two grades, one a high research octane(HRON), and the other low research octane (LRON), whereby the productionof these fuels by the OBS and their consumption are controlled fordelivery to an associated internal combustion engine in response to theengine's operating conditions.

Another object of the invention is to provide a multiple fuel deliverysystem for driving an internal combustion engine, wherein theconsumption of these fuels either individually or in various mixtures iscontrolled through use of an optimal RON map, the latter providingmapping of engine operating parameters such as torque, speed, gearratio, accelerator, and velocity, and so forth, to the RON fuel requiredby the internal combustion engine over a range of engine drive cycleconditions. Also, the control is programmed to vary the production ofthe LRON and HRON from the OBS as a function of the fuel consumption bythe engine at any given time.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present invention are described withreference to the drawings, in which like items are identified by thesame reference designation, wherein:

FIG. 1 is a simplified block schematic diagram of a fuel managementsystem for one embodiment of the invention;

FIG. 2 shows an optimized research octane number (RON) map plottingtorque versus engine speed for showing under ideal circumstances, thefuel RON for providing maximum engine performance for a particularcombination of torque value and engine speed, for a preferred embodimentof the invention;

FIG. 3 shows a flowchart for a control algorithm for an embodiment ofthe invention;

FIG. 4A shows a block schematic diagram of a fuel management system forone embodiment of the invention;

FIG. 4B shows a block schematic diagram of a fuel management system foranother embodiment of the invention;

FIG. 4C shows a block schematic diagram of a fuel management system foranother embodiment of the invention;

FIG. 5 shows a flowchart for an algorithm for another embodiment of theinvention in which torque and speed requirements of an engine can be metthrough use of low research octane number (LRON) fuel alone;

FIG. 6 is a plot of torque versus engine speed relative to fuelconsumption and the fuel utilized, for an embodiment of the invention;

FIG. 7 shows a simplified block schematic diagram of a fuel managementsystem for another embodiment of the invention;

FIG. 8 shows a longitudinal cross sectional view detailing variousaspects of the design for a two-way piston accumulator for an embodimentof the invention;

FIG. 9 shows a simplified block schematic diagram of a membraneseparation process using a mixed vapor liquid feed, for an embodiment ofthe invention;

FIG. 10A shows a pictorial view of a polymer-coating inorganic membranefor separating aromatic and aliphatic compounds, for a preferredembodiment of the invention; and

FIG. 10B shows an enlarged view of a portion of the front end of thepolymer-coated inorganic membrane of a 10A.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, a simplified block diagram of a fuelmanagement system for one embodiment of the invention is shown. A maintank 2 for retaining an intermediate grade of Research Octane Number(RON) fuel is included in the associated vehicle. In this example, theintermediate RON fuel is also designated as IRON. A variable ratio pump24 is operable for delivering the IRON fuel from the main tank 2 to anonboard separation (OBS) unit 4. The OBS unit 4 is operable forseparating the IRON fuel into two grades, one being a high researchoctane (HRON) grade fuel, and the other being a low research octane(LRON) fuel. The HRON fuel is delivered from OBS unit 4 to an HRON fueltank 8. The OBS unit 4 can be provided by separation devices usingsilica gel, distillation, membranes, and coated ceramic monoliths, forexample. The preferred embodiments for an OBS unit 4 will be discussedin greater detail below. In the following discussion, for purposes ofexample, OBS unit 4 uses a membrane separator providing HRON aspermeate, and LRON as retentate. Also, as will be described in furtherdetail below, the present system provides for both control of the rateof production of the HRON and LRON fuel via the feed rate of IRON fuelto the OBS unit 4, in combination with consumption control based onavailability of stored HRON fuel and mechanisms for minimizingcontamination of main tank fuel with LRON fuel. Such control is providedcontinuously over the various cycles of operation of the engine 10.

A controller 14, such as a microprocessor, for example, is programmed tocontrol operation of the present system. A liquid level sensor 3 isprovided in the main tank 2, and monitored by the controller 14.Similarly, a liquid level sensor 9 is provided in the tank 8 storingHRON fuel, with the sensor 9 being monitored by controller 14. Also, inthis example, the controller 14 is operable for controlling a pressuredifferential, such as an overflow valve or pump 16, for delivering HRONfuel from OBS unit 4 to the main tank 2 at times that the HRON tank 8 iscompletely filled with fuel; a pump 6 for delivering HRON fuel from OBSunit 4 to HRON tank 8; a pump 18 for delivering HRON fuel from tank 8back to the OBS unit for recycling; a pump or valve 20 for deliveringHRON fuel from tank 8 to a fuel injector system 12 of engine 10; avariable rate pump 22 for delivering LRON fuel from OBS unit 4 to thefuel injector system 12; a variable rate pump 24 for delivering IRONfuel to OBS unit 4; and a pump 26 for transferring excess LRON fuel fromOBS unit 4 to the main tank 2. It should be noted that in certainapplications, pumps such as 16, 6, 18, 22, and 26 can be replacedthrough use of gravity or pressure gradient feed transfer of theassociated fuel.

During operation of the associated vehicle, depending upon the driver'srequirements or engine load conditions at any time, fuel from HRON tank8 and the LRON stream is delivered to the engine 10 by fuel injectorsystem 12 in a given ratio. Note that the fuel injector system 12 mayinclude a plurality of fuel injectors. Also, at certain times duringoperation of the engine 10 IRON fuel from the main tank 2 can bedirectly delivered to the fuel injector system 12 via pump 26 andvariable rate pump 22. In this regard pump 26 can be a bidirectionalpump or other suitable mechanism. Typically, the fuel mixture deliveredto the fuel injector system 12 may include a given ratio of HRON andLRON fuels, or IRON and HRON fuels, or IRON and LRON fuels. Through useof the separation of the IRON fuel into HRON and LRON grades of fuelsboth more efficient fuel usage by engine 10 is attained, and shortbursts of high engine power operation is provided through injection of agreater amount of HRON into the engine 10. More specifically, dependingupon the load requirements of engine 10 at any given time, and also uponthe availability of each of the three fuels in this example, maximizingefficient operation of engine 10 may at certain times require a greateramount LRON fuels, at other times a greater amount of HRON fuel, and ifat any given time LRON fuel in the retentate stream is insufficient tomeet the engine's demands, or HRON fuel from tank 8 is not available,the deficit is made up through use of IRON fuel from main tank 2. Also,if the OBS unit 4 over produces HRON or LRON fuels, the excess amountsthereof are returned to the main tank 2, as shown by the dashed orbroken lines. Note that the pumps and/or valves mentioned above areprovided for purposes of example only, and any other mechanisms that canprovide the associated fuel delivery including gravity are meant to beincluded alternatively.

An Optimum RON Map is shown in FIG. 2 for mapping engine torque outputagainst engine speed against the level of RON fuel required by theengine for optimal or most efficient operation. This mapping isrepresented by the following equation:RON ^(ideal) =f(Torque, speed, gear ratio, accelerator, velocity)  (1).For ideal or optimal operation of engine 10, it should be provided withthe proportion of fuel specified by the map of FIG. 2. However, when oneof the normally available types of RON fuel is unavailable, controller14 is programmed to deviate from the optimum RON map. Note that theoptimal RON map of FIG. 2 was developed from a “Los Angeles 4” drivecycle, in this example. Also, in this example, the IRON fuel can be 91RON, the HRON fuel 103 RON, and the LRON 88 RON. However, the inventionis not meant to be limited to these RON fuel values.

In a preferred embodiment of the invention, the controller 14 isprogrammed to match the requirements of the driver of an associatedvehicle to the production characteristics of the OBS unit 4. It ispossible to control the present system in three different manners, asfollows:

-   -   The feed rate of the OBS unit 4 can be varied through use of a        variable pump 24 from 0.5 to 1.5 grams per second, for example.        In this manner, the production rate of the OBS unit 4 is        controlled. Note that the obtainment of such feed rate variation        is not meant to be limited to use of a variable rate pump,        whereas other mechanisms may also be utilized.    -   Through a recycle mechanism, the quantity of HRON fuel that is        recycled to the OBS unit 4 can be varied within certain limits.        For example, a variable rate pump 18 can be controlled for        varying the HRON recycle rate from 0 to 0.4 grams per second        (g/s) for the present system, but this rate is not meant to be        limiting.    -   The engine 10 can at any instant in time draw HRON fuel from the        HRON tank 8, and/or stream for LRON fuel, and/or IRON fuel from        the main tank 2, in any proportion. In this example, the        proportion is under the control of the controller 14 operating        pump/valve 20, pump 22, and bidirectional pump 26.

In the preferred embodiment of the invention, the controller 14 isprogrammed to jointly control the instantaneous behavior of the OBS unit4 via control of the feed rate thereto of IRON fuel, as previouslymentioned, and the instantaneous demands of the engine 10 relative towhich fuels to mix and in what proportion. Further note that in thesystem of FIG. 1, the pumps 16 and 26 can be considered optional, if aspreviously mentioned, gravity feed or pressure differential is utilizedfor returning HRON and/or LRON fuel to the main tank 2.

The control algorithms illustrated herein are independent of the methodof separation employed, that is independent of the type of OBS unit 4utilized. As previously mentioned, the OBS unit 4 can be provided byboth a distillation method or by a membrane method for obtaining thedesired fuel separation. The present method is also applicable withmodification for utilizing an OBS unit 4 that separates the IRON fuelinto more than two grades of RON fuel.

The present inventors recognize that the control algorithm or algorithmsutilized must be capable of controlling the production rate of the OBSunit 4 to match the driver's requirements, that is the loading on theengine 10 at any given time. In other words, controller 14 must have theability to change the feed rate of IRON fuel to the OBS unit 4 in amanner increasing the feed rate should the engine 10 demand more fuel ofa particular type due to a driver's operating requirements. For the samereason, the controller 14 must have the ability to decrease the feedrate should that be necessary. Also, the controller 14 must beprogrammed to provide a fuel mixture that is matched to the presentproduction of the OBS unit 4. For example, if a driver requires arelatively large amount of HRON fuel, and the HRON tank 8 is empty, itis then necessary for the controller 14 to operate to feed LRON fuel,and/or IRON fuel from the main tank 2 to make up for the deficit of HRONfuel.

In the preferred embodiment, the controller 14 is programmed to thegreatest extent possible to match the LRON consumption rate by engine 10as closely as possible to the LRON production rate by OBS unit 4. Suchcontrol is necessary to minimize the return of LRON fuel to the maintank 2, in that such action tends to degrade the quality of the fuel inthe main tank. Such matching is also desirable to minimize any increasein the ratio, for example, membrane permeate flux to feed rate to thepoint that it degrades HRON fuel quality produced.

The development of the control algorithm for the preferred embodiment ofthe invention will now be described. The algorithm is based uponestablishing one or more thresholds for the fuel level of HRON fuel inHRON tank 8. It was determined that the HRON tank 8 should have at leastone threshold fuel level designated as HL for designating HRON lower.Optionally, another threshold level HLL, which is a lower fuel levelthan HL, stands for HRON lower lower. It is assumed that the controller14 is operable for increasing or decreasing the OBS unit 4 IRON feedrate at any given time, and that the flows produced by the OBS unit 4can be fed to the engine individually, or in any necessary mixturedepending upon the engine 10 operating demands. It is further assumedthat controller 14 has fast enough operation for modifying the fuelmixture or fuel delivered to the engine 10 in a seamless mannerundetectable by a driver of the vehicle.

The present system is operable for balancing the production andconsumption of LRON fuel over a successively short measuring time periodto substantially minimize, and preferably avoid, overflow of LRON fuelback to the main tank 2. This is accomplished by controlling the feedrate of IRON fuel to the OBS unit 4 to substantially insure at all timesthat the LRON production closely tracks the short term LRON consumptionthrough use of the formula:F=L+h  (2),wherein F is the gross feed rate (fresh feed of IRON from tank 2 plusHRON recycle from tank 8), L is the estimated average LRON consumptionrate, and h is the HRON total production rate, the latter being thepermeate flux when a membrane type OBS unit 4 is used. L can be directlymeasured at the engine 10 fuel injector system 12. However, with thepresent state of the art, it has been observed that this formula orequation cannot be satisfied instantaneously. The reason is that the OBSunit 4 presently available for use in an engineering prototype has aslow response time, in the order of minutes, compared to engine demandsthat typically are in the order of seconds or factions of a second. Toovercome this present problem, time averaging must be applied to the OBSunit 4 feed rate setting, through use of either exponential smoothing ora windowing mechanism, for example. For a membrane based separationunit, the membrane can be designed so that the permeate flux h changesvery slowly over a time frame of months or even years. The fluxvariation can be “hard-coded” into the controller 14 as anapproximation, thereby permitting the feed rate F to be controlledpurely as a function of a single variable, mainly the LRON consumption.Alternatively, the flux can be estimated through use of changes in thelevel of HRON fuel in tank 8 in conjunction with the HRON consumptionrate. In a preferred embodiment, the controlled mechanism is furtherprogrammed to monitor when the level of IRON fuel in the main tank 2drops to a predetermined low level, such as 10% to 20% of capacity, toreduce the feed rate of IRON fuel from main tank 2 to the OBS unit 4 toa minimum value, while at the same time meeting the HRON requirements ofthe engine 10 by feeding IRON fuel from the main tank 2 to the engine10, to make up for any insufficiency of HRON fuel engine requirement ata given time. Through use of this extended control programming ormechanism, the degradation of the IRON fuel in the main tank 2 isminimized at times when the IRON fuel is most susceptible to degradationby return of LRON fuel to the main tank 2, due to the low level of IRONfuel thereof.

Programming of the controller 14 in order to provide consumption controlwill now be described. When the level of HRON fuel in tank 8 is higherthan a predetermined threshold level designated HL, the actual RON valueof the fuel used (as set by the proportion of LRON and HRON fuels used)is the same as that specified by the optimum RON map of FIG. 2, asrepresented by the following equation:RON^(actual)=RON^(ideal)  (3).Consumption control is necessitated when the level of HRON fuel in tank8 decreases to a level where the preferred control strategy is to useLRON or IRON fuel at times that engine 10 actually requires HRON fuel,in order to minimize the possibility of the HRON fuel in tank 8 beingtotally depleted. In order to obtain this control, a suitably modifiedRON map combined with control of the retardation of the engine sparkwhen fueling a spark ignition internal combustion engine, in a mannerthat is inconsequential to a driver. The basis for the control can alsobe provided for a compression combustion ignition engine (diesel orHCCI, for example) by the additional parameter of cetane number and anideal cetane number map. The actual control, in addition to use of theideal cetane number map, can be provided by appropriate parameters suchas valve timing, injection timing, intake air temperature orcombinations of these, to control knock. In either case, this can beaccomplished by employing a correction factor to the optimum RON map ofFIG. 2 at times when the level of HRON fuel in tank 8 drops below levelHL but is above threshold level HLL, the correction factor being appliedas shown in the following equation:RON^(actual)=αRON^(ideal)  (4),α=g(torque, speed, gear ratio, accelerator velocity)  (5).Note that in this control example, the correction factor α can be madeto depend on a numbers of engine parameters, including gear ratio andthe accelerator velocity, as shown above in order to rapidly accommodatethe RON requirements of engine 10. For example, if at a given timeengine 10 is in a high acceleration mode, when use of HRON fuel ispreferred, α can be set close to 1. Under other engine operatingconditions, LRON or IRON fuel can be substituted in larger quantitieswith the necessary level of spark retardation or advance such as withhigh speed/high fuel consumption. In this latter case, α is less than 1,which may result in a temporary reduction in fuel efficiency. Similarly,in a high acceleration mode for a compression combustion ignition engine(diesel or HCCI, for example), the control is effected through anexamination of the cetane number required by the engine. If the optimumcetane number is not available, this can be inferred by sensing thenoise due to knocking, whereby if the noise is excessive, it can bereduced by changing the valve timing, etc. When the level of HRON fuelin tank 8 is less than the level HLL, it is preferred to avoid anyfurther use of HRON fuel, in order to prevent damage to various enginecomponents, such as pump wear, and so forth. At such times, thecontroller 14 is programmed to operate the fueling system to provideeither LRON fuel from the retentate stream, and/or IRON fuel from themain tank 2. It should be noted that the control algorithm describedabove in equations (4) and (5) can be modified to be operable for morethan two predetermined levels of HRON fuel in tank 8. For conventionaldiesel engines, the following equation “(6)” can be used to balancecetane number along with operating conditions to reduce dieselparticulate matter:δPM=C ₁ ΔCN+C ₂ ΔA-Ring+C ₃ ΔN-Ring  (6)

-   -   where, δPM: PM (particulate matter) fraction reduction relative        to TF-ao        -   Δ: difference with respect to TF-ao CN: cetane number        -   A-Ring: aromatic rings (wt %)        -   N-Ring: naphthene rings (wt %)        -   Ci: regression coefficient (i=1, 2, 3)            -   C₁=0.0055            -   C₂=0.017            -   C₃=0.0065            -   TF: TF-series fuels

The algorithm of equations (4) and (5) as described above, is depictedin a flowchart in FIG. 3. With reference to FIG. 3, controller 14 isprogrammed to enter step 300 for initiating the subroutine shown. Instep 301, the output of the level sensor 9 is monitored by controller 14to determine whether the level of HRON fuel designated as H_(Hi) (HRONfuel content or level in tank 8) is less than H_(LL) (HRON fuel lowerlevel limit). If the answer is yes, then step 302 is entered for settingα to zero. Alternatively, if in decision step 301 the answer is no, thenstep 303 is entered, which is a decision step for determining whetherH_(Hi) is less than H_(L) (where H_(L) is a low level of HRON fuel intank 8 that is higher than H_(LL)). If in step 303 the answer is no,then step 304 is entered for setting α=1. Alternatively, if in decisionstep 303, the answer is yes, step 305 is entered for setting α equal toa value determined by the function of torque, speed, gear ratio, and soforth, where α will be greater than or equal to zero and less than orequal to 1. Step 306 is entered into after either one of the steps 302,or 305, or 304 are carried out, and the equations shown are calculated.In the equations shown, α is the correction factor as previouslymentioned, R_(Hitrg) is the HRON injection ratio, R_(Hiopt) is theoptimal HRON injection ratio as obtained from the optimum RON map ofFIG. 2, Q_(Hi) is the HRON fuel consumption rate, Q_(T) is the totalfuel being consumed, R_(Hitrg) is the actual HRON fuel injection ratio,Q_(Lo) is the LRON fuel consumption, Q_(T) is the total fuelconsumption, F is the feed rate which represents the sum of the IRONbeing fed to OBS unit 4 and the HRON being recycled, Q_(Lo) is the LRONfuel consumption, and h is the membrane flux.

In FIG. 4A, a preferred embodiment of the invention is shown for a fuelmanagement system, the operation of which will now be described. IRONfuel 1 contained in the main tank 2 is drawn through a filter 7 andpressurized by means of pump P1 against pressure regulators R1 and R2.In this example pressure regulator R1 was set to maintain a 100 kpapressure differential above R2. Pressure regulator R2 was set tomaintain a pressure of 200 kpag. Therefore, the pressure provided bypump P1 was ˜300 kpag. The pressurized IRON fuel 1 flow rate is set byflow controller FC-1 to the OBS separation unit 4. Excess pressurizedIRON fuel 1 is returned to the main tank 2 through pressure regulatorR2.

Separated HRON fuel 17, and LRON fuel 28, from the OBS unit 4 aredirected to the engine fuel injectors DFI (direct fuel injectionsystem), and PFI (port fuel injection system), or to the storage volumesshown as accumulator 74 and HRON tank 8. LRON fuel 28 is provided to theDFI injection system on demand. Excess LRON fuel 28 is directed to theaccumulator 74. IRON fuel 1 displaced from the accumulator 74 isreturned to the main tank 2 through the secondary pressure regulator R2.At the limit of the accumulator 74 volume, excess LRON fuel 28 flowsinto the main tank 2 along with excess IRON fuel 1 through pressureregulator R2. If demand for LRON fuel 28 exceeds the OBS unit 4production rate, additional LRON fuel 28 and/or IRON fuel 1 is providedby means of the accumulator 74. A check valve 29 prevents backflow tothe OBS unit 4.

HRON fuel 17 produced by the OBS unit 4 is delivered to the HRON tank 8by means of an eductor pump 15, or other suitable means. The HRON fuel17 in the HRON tank 8 is pressurized by means of pump P2 after passingthrough a filter 13 with the pressure controlled by pressure regulatorR3. Excess pressurized HRON fuel 17 returns to the HRON tank 8 throughR3. The pressurized HRON fuel 17 is provided to the port fuel injector(PFI) and to the eductor pump 15, with excess fuel returning to the HRONtank 8. An overflow tube 19 is provided to allow excess HRON fuel 17accumulated in the HRON tank 8 to overflow into the main tank 2. A floattype level sensor L3 provides a continuous measure of the level of HRONfuel 17 in the HRON tank 8.

In the fuel management system of FIG. 4A, the accumulator 74 is a pistontype including a moveable piston 72. The fuel management system of FIG.4B is substantially identical to that of FIG. 4A. However, in the systemof FIG. 4B, rather than a piston accumulator 74 being used, anaccumulator volume 76 is utilized, and can be provided by a tubularcavity, for example. As previously mentioned, in the preferredembodiment, the piston accumulator 74 is utilized. When cost is afactor, a tubular design is most preferred.

With reference to FIG. 4C, a simplified fuel management system withpassive recycle will now be described for another embodiment of theinvention. This embodiment provides for managing fuel flow from the OBSunit 4 with essentially no dilution of the main tank IRON fuel 1 byexcess LRON fuel 28 or HRON 17. IRON fuel 1 contained in the main tank 2is drawn through filter 7 and pressurized by means of pump P1 againstpressure regulators R1 and R2. Pressure regulator R1 is set to typicallymaintain a 25 to 100 kpa pressure differential above R2. Pressureregulator R2 is typically set to maintain a pressure of 200-600 kPag.The pressure provided by pump P1 is typically 400 kPag. Pressurized IRONfuel 1 flow rate is set by flow controller FC-1 to the OBS separationunit 4. Excess pressurized IRON fuel 1 is returned to the inlet of thepump P1 through pressure regulator R2 by directing the flow to astandpipe 21, and therefrom into a filter shroud 77.

Alternatively, the excess HRON fuel 17 return can be connected directlyto a first inlet port 90 of the fuel suction pipe or standpipe 21, anddirectly therefrom to an inlet or fuel feed port (not shown) of pump P1.Also, alternatively, excess LRON fuel 28 return can be connected viapressure regulator R2 to a second port 92 of the fuel suction pipe orstandpipe 21, and directly therefrom to an inlet or fuel feed port (notshown) of pump P1. Note that port 92 can also receive excess IRON fuel 1via pressure regulator R2.

Separated HRON fuel 17 and LRON fuel 28 from the OBS unit 4 are directedto the engine fuel injectors PFI, DFI, respectively, or to the storagevolumes provided by accumulator volume 76, appropriately sized tominimize mixing of the two fuels, and HRON tank 8, as shown. LRON fuel28 is provided to the direct fuel injection system DFI on demand. ExcessLRON fuel 28 is directed into the storage volume provided by accumulator76. IRON fuel 1 displaced from the accumulator 76 is returned to theinlet of the pump P1 through pressure regulator R2 by directing the flowto the standpipe 21 and filter shroud 36.

At the limit of the accumulator 76 volume, excess LRON fuel 28 flowsinto standpipe 21 along with excess IRON fuel 1 through pressureregulator R2. If demand for LRON fuel 28 exceeds the OBS unit 4production rate, additional LRON fuel 28 and/or IRON fuel 1 is providedby means of the volume of the accumulator 76. A check valve 29 preventsbackflow to the OBS unit 4.

HRON fuel 17 produced by the OBS unit 4 is delivered to the HRON tank 8by means of an eductor pump 15, or other suitable means. The HRON fuel17 in the HRON tank 8 is pressurized by means of pump P2 after passingthrough filter 13 with the pressure being controlled by pressureregulator R3. Excess pressurized HRON fuel 17 returns to the HRON tank 8through regulator R3. The pressurized HRON fuel 17 is provided to thePFI port fuel injector and to the eductor pump 15, with excess fuelreturning to the HRON tank 8. An overflow tube 19 is provided to allowexcess HRON fuel 17 accumulated in the HRON tank 8 to overflow intostandpipe 21. Excess HRON fuel 17 is recycled to the OBS unit 4 by beingdrawn from the standpipe 21 though filter shroud 36 and filter 7 bymeans of pump P1 and flow control FC-1. A float type or other suitablelevel sensor L3 provides a measure of the level of HRON fuel 17 in theHRON tank 8.

In FIG. 8, an example of the design details for accumulator 74 for theembodiment of the invention of FIG. 4A is shown, but is not meant to belimiting in that other accumulator designs can be used. The accumulator74 consists of a piston 72 and cylindrical housing 77 having a nominaldisplacement volume of 750 cm³ as used in experimental vehicle tests.The piston 72 uses Teflon® sealing rings 78 providing low resistance tomovement such that the piston travels freely with minimal, i.e. <10 kPa,of differential pressure. The piston 72 incorporates a modified checkvalve 80, Swagelok SS-2-C2-1 or equivalent, which provides sealing ofthe piston 72 during travel, but opens to allow flow of IRON fuel 1 andLRON fuel 28 at the opposing ends of travel limited by the cylinderfaces 82 and 84, respectively. With flow in the direction associatedwith the normal opening function of the check valve 80, it opens toallow flow through the piston 72 when the piston 72 travel is stopped bythe cylinder face 84, providing IRON fuel 1 to the DFI fuel injectorfrom the main tank 2 as required. When excess LRON fuel 28 is produced,the piston 72 travels in the opposite direction with the piston sealedby the check valve 80 until reaching the opposite cylinder face 82. Asthe piston 72 approaches the cylinder face 82, a pin 86 adjusted to pushopen the check valve 80 as the piston approaches the cylinder face 82 isengaged to allow flow of LRON fuel 28 to the main tank against the backpressure of regulator R2 (not shown, see FIG. 4A).

With further reference to the flowchart of FIG. 3 showing operation of acontrol algorithm for controller 14, note that during times that thetorque and speed requirements of the engine 10 can be met by use of LRONfuel alone, then α can be set to zero as shown in step 305(B) of themodified flowchart of FIG. 5. More specifically, as shown in theflowchart of FIG. 5, compared to that of FIG. 3, step 305 of FIG. 3 hasbeen replaced by Steps 305(A) and 305(B) in FIG. 5. In step 305(A) adecision is made to determine whether T_(demand) (engine torque, speed,gear ratio, etc.) is less than LRON WOT (maximum torque of engine 10using only LRON fuel). If the answer is no, as in the previousalgorithm, step 304 is entered. Alternatively, if the answer is yes,step 305(B) is entered for setting α=0. Otherwise, the operation of thealgorithm of FIG. 5 is the same as that previously described for thealgorithm of FIG. 3.

A plot of torque versus engine speed for engine 10 relative to fuelconsumption is shown in FIG. 6. As shown maximum fuel consumption occurswhen HRON fuel is being used to maximize torque output of engine 10.Also as shown, when only LRON fuel is being used to maximize the torqueof engine 10, high fuel consumption occurred in the higher engine speedversus torque areas of the curve, whereas if engine speed and torque arereduced to below a threshold shown as “C”, lower fuel consumption isrealized. Minimal fuel consumption is obtained when the engine speed andtorque are below a threshold “D” as shown in the curve.

In FIG. 7, the fuel management system of FIG. 1 has been expanded toshow a simplified practical system for delivering multiple grades of RONfuel to an engine. The controller 14 of FIG. 1 is not shown in FIG. 7,but is considered to be included therein for controlling operation ofthe various mechanical and electromechanical components of the presentsystem. In this example, the HRON tank 8 has been incorporated into aportion of the main tank 2, as shown. The pump P2 is incorporated withinthe HRON tank 8, as shown. The pump P1 is incorporated within the maintank 2. Also, a fuel storage volume provided by an accumulator 74 isincluded in the main tank 2, and operative to retain a portion of LRONfuel that has been produced by the OBS unit 4 but not consumed by theengine 10 at any given time. Any LRON fuel contained within theaccumulation volume of accumulator 74 is available for delivery to theengine 10. In one embodiment the accumulation volume can merely beprovided by a tube serving as an accumulator 74, and having a volume inthis example of 100 cc (cubic centimeters), which volume is not meant tobe limiting. Also, in another embodiment of the invention, theaccumulation volume can be provided by a two-way piston accumulator 74,as shown in FIGS. 4A and 8, respectively. The two-way piston accumulator74 is described in detail above with reference to FIG. 8.

With further reference to FIG. 7, a flow controller FC is installed inthe IRON fuel path between pump P1 and an integrated heat exchanger 34.Note that IRON fuel flow is indicated by reference 36, LRON by reference38, and HRON fuel by reference 40. An eductor 42 receives pressurizedHRON fuel 40 for producing a vacuum for drawing HRON permeate or fuel 40from OBS unit 4. A one-way valve 44 is included in the LRON fluidpathway 38 for preventing LRON fuel from flowing back to the integratedheat exchanger 34. The typically warm temperature HRON fuel 40 from P2is passed through an air fin cooling tube 46 to maintain the temperatureof HRON tank 8 near ambient. A heat pipe 48 is included for preheatingthe IRON fuel 36 before it is introduced into the OBS unit 4. In thisexample, the engine 10 includes a direct fuel injector DFI for injectingLRON fuel 38 into an associated cylinder of an engine 10, and a portfuel injector PFI for injecting HRON fuel 40 into the associatedcylinder of the engine 10. Engine 10 exhaust gases are passed through acatalytic converter 54, a heat pipe heat exchanger 56, and a mufflerexhaust pipe 58, as shown. A portion of the exhaust gas energy isutilized for heating the heat pipe 48. Also, the integrated heatexchanger 34 permits heat exchange between IRON fuel 36 being passedthrough to the OBS unit 4, and the HRON and LRON fuels 40, 38,respectively, received from the OBS unit 4 and passed through in theopposite direction to the flow of the IRON fuel 36 therethrough. Notethat the use of exhaust gas energy for heating is not meant to belimiting, in that other heating mechanisms can be used. The HRON fuel 40produced is stored within the HRON tank 8, as previously explained.Also, note that the reference numerals 41 and 47 each designate pipe orconduit couplings.

Note that the fuel management system of FIG. 7 can be utilized throughappropriate flow control mechanisms, to maintain necessary operatingtemperature of the fuels to effect desired separation. For example, ifthe measured temperature of the IRON fuel to the OBS unit 4 exceeds apredetermined limit temperature, the IRON fuel 36 rate will be variedvia flow controller FC to maintain the desired temperature.

In FIG. 9, a simplified block schematic diagram is shown of componentsof the present system of FIG. 7 utilizing a membrane separation devicefor OBS unit 4 as taught in Provisional Application U.S. Ser. No.60/830,914, filed on Jul. 14, 2006, for an “Improved Membrane SeparationProcess Using Mixed Vapor-Liquid Feed.” The teachings of the latter areincorporated herein by reference to the extent they do not conflictherewith. More specifically, with regard to the illustrated OBS unit 4of this embodiment, the integrated heat exchanger 34 provides forpartially vaporizing IRON fuel to maintain dual feed states relative tothe IRON fuel feed, which is fed to the OBS unit 4 as both liquid andvapor. The term “partially vaporized” means there is sufficientvaporization to provide the optimal vapor liquid mixture to themembrane. The liquid portion 60 contacts and wets the pervaporizationmembrane 62. The IRON liquid 60 has an increased content of thepreferred permeate (relative to the IRON feed 36), while the vapor 61phase has an increased content of the preferred retentate. In thisexample, the preferred permeate is HRON fuel, and the preferredretentate is LRON fuel.

The pervaporization membrane 62 is a selective membrane, selected topreferentially permeate the preferred permeate. For this application, anaromatic selective membrane such as described in U.S. Pat. No. 5,670,052can be employed, for example. The teachings of this Patent areincorporated herein by reference to the extent that they do not conflictherewith. The selective pervaporization membrane 62 can include physicalporous support means (not shown) such as Gortex™, for example, capableof providing physical support of the selective pervaporization membrane62 under the temperature, pressure, and other conditions to beencountered. Alternative supports can include sintered metal or ceramicporous media. A preferred support means includes an asymmetric porousmedia such as a porous ceramic tube or monolith having a microporoussurface material, as will be described for another embodiment of theinvention for the OBS unit 4.

In a preferred embodiment for the illustrated OBS unit 4 design, across-linked polyimide-polyadipate membrane polymer supported on aporous ceramic support means provides the membrane 62. Suchconfigurations are taught in U.S. Provisional Application No.60/836,319, filed on Aug. 8, 2006, for “Polymer-Coated InorganicMembrane For Separating Aromatic And Aliphatic Compounds.” The teachingsof the latter are incorporated herein by reference to the extent thatthey do not conflict herewith. FIGS. 10A and 10B illustrate anembodiment from this Application that is considered a preferredembodiment for the present invention, and uses a tubular inorganicceramic substrate. In FIG. 10A, a tubular inorganic substrate 31 isincluded for the OBS unit 4 in this embodiment. The porous inorganicsubstrate 31 can comprise silica or alumina coated mullite, or siliconecarbide, or other suitable monolith structures, for example. As shown,in this example IRON fuel 36 is fed into a plurality of channels 33within the porous inorganic substrate 31. The surfaces of the channels33 can, in a preferred embodiment, comprise a porous inorganic materialwhose porosity differs from the bulk porosity of the substrate 31. Mostpreferably, the surface porosity of the channels 33 is less than orabout equal to the aggregate polymer size of the associated polymer. Aspreviously indicated, a cross-linked polyimide-polyadipate membranepolymer can be utilized. In FIG. 10B, an illustration of an explodedarea 35 of FIG. 10A, illustrates that the channels 33 include aninterior surface region 33A that may be formed by wash coating theinterior surfaces of the channels 33 of substrate 31 to form a silicatop coat, for example. The channels 33 having the optimal surfaceregions 33A are each coated with an associated polymer layer 37 to formthe required membrane system. As shown in FIG. 10A, permeate (HRON fuel40) from the membrane system is taken radially and retentate (LRON fuel38) exits axially, in this embodiment.

In summary, the present invention provides for controlling theproduction and consumption of fuel in a vehicle equipped with an OBSunit 4, and an HRON tank 8, from amongst other components. The presentsystem provides for producing HRON and LRON fuels from a feed of IRONfuel, and supplies the individual grade or a mix of the grades of fuelto the engine 10 as required by its operating state at a given time. Thesystem is adaptive to modifying the rate of production of the fuels inaccordance with the engine 10 demands.

The production rate control for the OBS unit 4 is provided bycontrolling the feed rate of the IRON fuel to the OBS unit 4 by settingthe feed rate equal to the LRON fuel use at a given time, combined withthe OBS unit 4 membrane flux. Typically, the membrane flux is estimated,and a measurement is continuously made of the amount of the LRON fuelbeing used by the engine at a given time. The production rate controlminimizes the main tank 2 degradation by lowering OBS unit 4 feed rateto a minimum value, whenever the level of IRON fuel in the main tank 2is below a predetermined threshold.

As further illustrated above, a consumption control algorithm providesfor reducing the consumption of HRON fuel during shortages of this fuelby providing correction factors to the optimum RON Map shown in FIG. 2.The correction factor, in the example given above, as α, provides foraccounting for the state of the engine when a fuel shortage occurs, andthe level in the HRON tank 8 is at a predetermined threshold value. Inthe instant where the present system is used with a spark ignitioninternal combustion engine, the associated control system may adjustspark advance/retardation as required for insuring proper engineperformance. Also, as indicated above, whenever the level of HRON fuelin tank 8 drops to below a predetermined level HLL, the controller 14 isoperative to terminate any further delivery of HRON fuel to the engine10, in order to prevent damage to various of the system components, suchas pumps. Also, as previously indicated, the present system can bemodified to be operative with more than two or three RON values of fuel,as previously described.

Note that the IRON fuel can also be designated as a regular grade fuelhaving an intermediate autoignition temperature (IAT) fuel. Similarly,the HRON fuel can be designated as a low autoignition temperature (LAT)fuel whose autoignition temperature is lower than that of IAT fuel.Lastly, the LRON fuel can be designated as a high autoignitiontemperature (HAT) fuel whose autoignition temperature is higher thanthat of IAT fuel.

Also note that FIG. 2 can be modified to provide an optimal autoignitionfuels map to determine the fuel requirements in terms of autoignitiontemperature values. The optimal autoignition temperature map can bedeveloped from the following equation:Autoignition Temperature^(ideal) =f(Torque, Speed, Gear ratio,accelerator velocity)  (7)The engine operating requirements can be matched to a plurality ofmarket fuels by direct or indirect measurement of the quality of the LATfuel produced by the OBS unit from each of the fuels.

Although various features of the present invention have been shown anddescribed herein, they're not meant to be limiting. Those of skill inthe art may recognize certain modifications to these embodiments, whichmodifications are meant to be covered by the spirit and scope of theappended claims. For example, in operating the OBS unit 4, thepermeation rate can be set in excess of normal HRON demands, whereby theexcess is passively recycled by overflow back to the OBS unit 4, asshown in FIG. 1, resulting in an increase in the RON value of the HRONfuel produced. Also, the present invention can be extended by matchingthe engine requirements to a plurality of market fuels by direct orindirect measurement of the quality of the HRON fuel being produced bythe OBS unit 4. It also should be noted that the OBS unit 4 is notlimited to the embodiments taught above, and can be provided by eitherone of silica gel, distillation, membranes, and coated ceramicmonoliths, and so forth. In addition, although this invention isprimarily described above in terms of control of the autoignitionproperty RON in association with a plurality of different grades ofgasoline selectively fed to an internal combustion spark ignitionengine, those skilled in the art should recognize that the variousembodiments of the present invention are equally applicable to dieseland other internal combustion compression ignition engines, where thefuel ignition property is expressed in cetane number rather than RON.For example, with regard to High Compression Combustion Ignition (HCCI)engines, the inventors believe a 15 to 85 cetane number range of dieselfuels would be usable, whereby at high engine load fuels having lowercetane number would be used, and at low engine loads fuels having highercetane numbers would be used. However, the range of cetane numbers isnot meant to be limiting, and is dependent upon the type of dieselengine being used.

1. A method for managing the delivery of fuel to an internal combustionengine of a vehicle, comprising the steps of: filling a main tank ofsaid vehicle with a predetermined amount of regular fuel having anintermediate research octane number (IRON); controllably delivering IRONfuel from said main tank to an on-board separation (OBS) unit of saidvehicle, said OBS unit being operable for separating said IRON fuel intoa high research octane number (HRON) fuel and a low research octanenumber (LRON) fuel, higher and lower than said IRON fuel, respectively;delivering HRON fuel from said OBS unit to an HRON tank of said vehicle;monitoring the operational requirements of said engine at any giventime; controllably and selectively delivering either HRON fuel from saidHRON tank, or LRON fuel directly from said OBS unit, or a mixturethereof to said engine, in response to said monitoring step; measuringthe HRON fuel level in said HRON tank; controlling both the productionof said HRON and LRON fuels by said OBS unit, and the consumption ofthese fuels by said engine, in response to both said HRON levelmeasuring step, and to said monitoring step, whenever the level of fuelin said HRON tank is within predetermined limits; controlling theproduction and consumption of HRON and LRON fuels in accordance with apredetermined algorithm, whenever the level of fuel in said HRON tankdecreases to a predetermined lower limit; and recirculating HRON fuelfrom said HRON tank to either one or both of said OBS unit and said maintank, whenever the level of fuel in said HRON tank exceeds apredetermined high limit.
 2. The method of claim 1, wherein saidrecirculation step further includes; installing a fuel supply pump insaid main tank, said pump having an inlet port for receiving fuel, andan outlet port for delivering fuel to said OBS unit; installing asuction pipe in said main tank having a first port for receiving excessHRON fuel from said HRON tank; and delivering excess HRON fuel from saidsuction pipe to said inlet port of said fuel supply pump.
 3. The methodof claim 2, wherein said recirculation step further includes: installinga second port in said suction pipe for receiving excess LRON fuel fromsaid OBS unit; and delivering excess LRON fuel from said suction pipe tosaid inlet port of said fuel supply pump.
 4. A method for managing thedelivery of fuel to an internal combustion engine of a vehicle,comprising the steps of: filling a main tank of said vehicle with apredetermined amount of regular fuel having an intermediate researchoctane number (IRON); controllably delivering IRON fuel from said maintank to an on-board separation (OBS) unit of said vehicle, said OBS unitbeing operable for separating said IRON fuel into a high research octanenumber (HRON) fuel and a low research octane number (LRON) fuel, higherand lower than said IRON fuel, respectively; delivering HRON fuel fromsaid OBS unit to an HRON tank of said vehicle; monitoring theoperational requirements of said engine at any given time; controllablyand selectively delivering either HRON fuel from said HRON tank, or LRONfuel directly from said OBS unit, or a mixture thereof to said engine,in response to said monitoring step; measuring the HRON fuel level insaid HRON tank; controlling both the production of said HRON and LRONfuels by said OBS unit, and the consumption of these fuels by saidengine, in response to both said HRON level measuring step, and to saidmonitoring step, whenever the level of fuel in said HRON tank is withinpredetermined limits; and controlling the production and consumption ofHRON and LRON fuels in accordance with a predetermined algorithm,whenever the level of fuel in said HRON tank decreases to apredetermined low limit.
 5. The method of claim 4, further including thestep of: controllably delivering HRON fuel from said OBS unit to saidmain tank whenever said HRON tank is filled to a predetermined level. 6.The method of claim 4, further including the step of: controllablydelivering LRON fuel from said OBS unit to an accumulation space,whenever said engine does not at a given time require the total amountof LRON fuel being produced by said OBS unit.
 7. The method of claim 4,further including the step of: controllably delivering IRON fuel fromsaid main tank to said engine whenever HRON and LRON fuels areunavailable.
 8. The method of claim 4, wherein said monitoring stepincludes the steps of: sensing the torque versus engine speed of saidengine at any given time; and using an optimal RON map to determine theRON fuel requirement from the sensed torque and engine speed.
 9. Themethod of claim 8, further including the step of developing said optimalRON map from the following equation:RON. ^(ideal) =f(Torque, speed, gear ratio, accelerator, velocity). 10.The method of claim 4, further including the step of matching the engineoperating requirements to a plurality of market fuels by direct orindirect measurement of the quality of the HRON fuel produced by saidOBS unit from each of the fuels.
 11. The method of claim 4, furtherincluding the step of controllably recycling HRON fuel from said HRONtank to said OBS unit in the event of filling said HRON tank to apredetermined level.
 12. The method of claim 4, wherein said step ofcontrollably delivering IRON fuel from said main tank to said OBS unit,includes the step of equating short term LRON fuel production by thelatter to short term LRON consumption by said engine via use of theformula:F=L+h wherein F is the gross mass feed rate (IRON fuel from main tankplus HRON fuel recycled from said HRON tank), L is the estimated averageLRON fuel consumption rate, and h is the HRON fuel total productionrate.
 13. The method of claim 4, further including the step ofterminating the delivery of HRON fuel to said engine if the levelthereof in said HRON tank drops to below a predetermined level HLL. 14.The method of claim 6, further including the step of providing an opentube to serve as said accumulation space.
 15. The method of claim 6,further including the step of providing a two-way piston accumulator toserve as said accumulation space.
 16. The method of claim 15, furtherincluding the step of forming said accumulator to include: a housingenclosing said accumulation space; a piston located in said accumulationspace, and slideably moveable therein; and a two-way check valvecentrally located within said piston.
 17. The method of claim 4, furtherincluding the step of preheating said IRON fuel before its delivery tosaid OBS unit.
 18. The method of claim 4, further including the step ofdelivering LRON fuel to a direct fuel injector of said engine.
 19. Themethod of claim 18, further including the step of delivering IRON fuelto said direct fuel injector in the event of insufficient LRON fuelbeing available at a given time.
 20. The method of claim 4, furtherincluding the step of delivering HRON fuel to a port fuel injector ofsaid engine.
 21. The method of claim 8, further including the step of:applying a correction factor to said RON map in response to said levelmeasuring step indicating that the level of HRON fuel in said HRON tankhas dropped below a first threshold level HL, but is above a lower levelHLL.
 22. The method of claim 21, further including the step ofterminating the delivery of HRON to said engine in response to saidlevel measuring step indicating that the level of HRON fuel in said HRONtank has dropped to below H_(LL).
 23. The method of claim 4, furtherincluding the step of selecting said OBS unit from one of a group ofseparation mechanisms consisting of silica gel, distillation, membranes,and polymer coated ceramic monoliths.
 24. The method of claim 4, furtherincluding for providing said OBS unit, the steps of: forming a tubularporous inorganic ceramic substrate having a plurality of channelsextending inward from one end; coating the channels with an associatedpolymer; feeding said IRON fuel into said plurality of channels; takingsaid HRON fuel radially from said substrate; and taking said LRON fuelaxially from said substrate.
 25. The method of claim 4, furtherincluding the step of cooling said HRON and said LRON fuels after takingthem from said OBS unit.
 26. In a motorized vehicle including a mainfuel tank, an on-board separation (OBS) unit, a high research octanenumber (HRON) fuel tank, and an internal combustion engine, a method forselectively delivering fuel from one or a combination of said main tank,OBS unit, and HRON tank to said engine, comprising the steps of: fillingsaid main tank with a predetermined amount of fuel having anintermediate research octane number (IRON); controllably delivering fuelfrom said main tank to said OBS unit; operating said OBS unit to producean HRON grade fuel, and a low research octane number LRON fuel;delivering said HRON fuel from said OBS unit to said HRON tank;controllably delivering said LRON fuel in a retentate stream directlyfrom said OBS unit to said engine in a first mode of operation;controllably delivering HRON fuel from said HRON tank to said engine ina second mode of operation; sensing the level of HRON fuel in said HRONtank; controllably delivering HRON fuel from said OBS unit to said maintank, in response to said level sensing step, at times that said HRONtank is filled to a predetermined level with HRON fuel; controllablyrecycling HRON fuel from said HRON tank to said OBS unit, in response tosaid level sensing step, at times that said HRON tank is filled to apredetermined level; limiting the delivery of LRON fuel in saidretentate stream to said main tank; controllably delivering IRON fuelfrom said main tank to said engine in a third mode of operation; andcontrolling the production of HRON and LRON fuels by said OBS unit bothin response to said level sensing step, and to match the demand forthese fuels by said engine at any given time.
 27. A vehicle mounted fuelmanagement system for delivering individually and/or in differentmixtures a plurality of different grades of RON fuel to an associatedinternal combustion engine, comprising: a main tank for containing afuel having an intermediate research octane number (IRON); an on-boardseparation (OBS) unit receptive of IRON fuel, said OBS unit beingoperable for separating said IRON fuel into at least a high researchoctane number (HRON) fuel, and a low research number (LRON) fuel, higherand lower than said IRON fuel, respectively; flow control means forfeeding IRON fuel from said main tank to said OBS unit; an HRON tank forreceiving and containing HRON fuel from said OBS unit; means formeasuring the level of HRON fuel in said HRON tank; means forcontrollably and selectively delivering either HRON fuel from said HRONtank, or LRON fuel directly from said OBS unit, or a mixture thereof tosaid engine, in response to both said level measuring means, and theoperational requirements of said engine at any given time; and means forcontrolling the speed of said flow control means to obtain a feed rateof said IRON fuel to said OBS unit, to control the latter's productionof HRON and LRON fuels to match the demand for these fuels by saidengine at any given time.
 28. The fuel management system of claim 27,wherein said OBS unit is selected from one of a group of separationmechanisms consisting of silica gel, distillation, membranes, andpolymer coated ceramic monoliths.
 29. The fuel management system ofclaim 27, wherein said OBS unit includes: a tubular porous inorganicceramic substrate having a plurality of channels extending inward fromone end; and an associating polymer coated on said channels, saidchannels being configured for receiving IRON fuel from said pump,whereby HRON fuel can be taken radially from said substrate, and LRONfuel can be taken axially from said substrate.
 30. The fuel managementsystem of claim 27, further including: accumulator means connectedbetween said main tank and an LRON output port of said OBS unit, forproviding a storage space or volume for both storing excess LRON fuelproduced by said OBS unit, and providing a fluid pathway for fuel fromsaid main tank to be delivered to said engine in the even insufficientLRON and/or HRON fuels are available for delivery to said engine. 31.The fuel management system of claim 30, wherein said accumulator meansincludes an accumulator having an open storage volume.
 32. The fuelmanagement system of claim 30, wherein said accumulator means includes apiston accumulator.
 33. The fuel management system of claim 32, whereinsaid piston accumulator includes a two-way check valve for bothpermitting LRON fuel in said storage volume to be pushed out of saidaccumulator by movement of a piston in one direction, to help overcome adeficiency in LRON fuel at a given time, and for permitting IRON fuel tobe delivered to said engine when said piston moves opposite to said onedirection to make up for insufficient LRON fuel and/or HRON fuel. 34.The fuel management system of claim 27, further including: means forselectively delivering either LRON fuel to a direct fuel injector ofsaid engine, or IRON fuel to said direct fuel injector in the event ofan insufficiency of LRON fuel at any given time.
 35. The fuel managementsystem of claim 34, further including means for delivering HRON fuel toa port fuel injector of said engine.
 36. The fuel management system ofclaim 27, further including means for delivering HRON fuel to a portfuel injector of said engine.
 37. The fuel management system of claim27, further including: means for preheating IRON fuel before itsdelivery to said OBS unit.
 38. A method for managing the delivery offuel to an internal combustion engine of a vehicle, comprising the stepsof: filling a main tank of said vehicle with a predetermined amount ofregular fuel having an intermediate autoignition temperature (IAT);controllably delivering IAT fuel from said main tank to an on-boardseparation (OBS) unit of said vehicle, said OBS unit being operable forseparating said IAT fuel into a high autoignition temperature (HAT) fueland a low autoignition temperature (LAT) fuel, higher and lower thansaid IAT fuel, respectively; delivering LAT fuel from said OBS unit toan LAT tank of said vehicle; monitoring the operational requirements ofsaid engine at any given time; controllably and selectively deliveringeither LAT fuel from said LAT tank, or HAT fuel directly from said OBSunit, or a mixture thereof to said engine, in response to saidmonitoring step; measuring the LAT fuel level in said LAT tank;controlling both the production of said LAT and HAT fuels by said OBSunit, and the consumption of these fuels by said engine, in response toboth said LAT level measuring step, and to said monitoring step,whenever the level of fuel in said LAT tank is within predeterminedlimits; and controlling the production and consumption of LAT and HATfuels in accordance with a predetermined algorithm, whenever the levelof fuel in said LAT tank is not within predetermined limits.
 39. Themethod of claim 38, wherein said internal combustion engine consists ofa diesel type compression combustion ignition engine, whereby saidmethod further includes the steps of designating each of said IAT, LAT,and HAT fuel in terms of cetane number.
 40. The method of claim 39,wherein said diesel engine is an HCCI engine, said method furtherincluding the steps of: selecting said LAT fuel to have a cetane numberof 15; and selecting said HAT fuel to have a cetane number of
 85. 41.The method of claim 39, wherein said cetane numbers are selected inaccordance with the following equation:δPM=C ₁ ΔCN+C ₂ ΔA-Ring+C ₃ ΔN-Ring where, δPM: PM (particulate matter)fraction reduction relative to TF-ao Δ: difference with respect to TF-aoCN: cetane number A-Ring: aromatic rings (wt %) N-Ring: naphthene rings(wt %) Ci: regression coefficient (i=1, 2, 3) C₁=0.0055 C₂=0.017C₃=0.0065 TF: TF-series fuels.
 42. The method of claim 38, wherein saidengine is a spark ignition internal combustion engine, whereby saidmethod further includes the steps of designating each of said IAT, LAT,and HAT fuels in terms of RON (Research Octane Number).
 43. The methodof claim 38, further including the step of: controllably delivering LATfuel from said OBS unit to said main tank whenever said LAT tank isfilled to a predetermined level.
 44. The method of claim 38, furtherincluding the step of: controllably delivering HAT fuel from said OBSunit to an accumulation space, whenever said engine does not at a giventime require the total amount of HAT fuel being produced by said OBSunit.
 45. The method of claim 38, further including the step of:controllably delivering intermediate IAT fuel from said main tank tosaid engine whenever LAT and HAT fuels are unavailable.
 46. The methodof claim 38, wherein said monitoring step includes the steps of: sensingthe torque versus engine speed of said engine at any given time; andusing an optimal autoignition temperature fuels map to determine thefuel requirement in terms of autoignition temperature value from thesensed torque and engine speed.
 47. The method of claim 46, furtherincluding the step of developing said optimal autoignition temperaturemap from the following equation:Autoignition Temperature^(ideal) =f(Torque, speed, gear ratio,accelerator velocity).
 48. The method of claim 38, further including thestep of matching the engine operating requirements to a plurality ofmarket fuels by direct or indirect measurement of the quality of the LATfuel produced by said OBS unit from each of the fuels.
 49. The method ofclaim 38, further including the step of controllably recycling LAT fuelfrom said LAT tank to said OBS unit in the event of filling said LATtank to a predetermined level.
 50. The method of claim 38, wherein saidstep of controllably delivering IAT fuel from said main tank to said OBSunit, includes the step of equating short term HAT fuel production bythe latter to short term HAT consumption by said engine via use of theformula:F=L+h wherein F is the gross mass feed rate (IAT fuel from main tankplus LAT fuel recycled from said LAT tank), L is the estimated averageHAT fuel consumption rate, and h is the LAT fuel total production rate.51. The method of claim 38, further including the step of terminatingthe delivery of LAT fuel to said engine if the level thereof in said LATtank drops to below a predetermined level HLL.
 52. The method of claim44, further including the step of providing an open tube to serve assaid accumulation space.
 53. The method of claim 44, further includingthe step of providing a two-way piston accumulator to serve as saidaccumulation space.
 54. The method of claim 53, further including thestep of forming said accumulator to include: a housing enclosing saidaccumulation space; a piston located in said accumulation space, andslideably moveable therein; and a two-way check valve centrally locatedwithin said piston.
 55. The method of claim 38, further including thestep of preheating said IAT fuel before its delivery to said OBS unit.56. The method of claim 38, further including the step of delivering HATfuel to a direct fuel injector of said engine.
 57. The method of claim56, further including the step of delivering IAT fuel to said directfuel injector in the event of insufficient HAT fuel being available at agiven time.
 58. The method of claim 38, further including the step ofdelivering LAT fuel to a port fuel injector of said engine.
 59. Themethod of claim 46, further including the step of: applying a correctionfactor to said autoignition temperature fuels map in response to saidlevel measuring step indicating that the level of LAT fuel in said LATtank has dropped below a first threshold level HL, but is above a lowerlevel HLL.
 60. The method of claim 59, further including the step ofterminating the delivery of LAT fuel to said engine in response to saidlevel measuring step indicating that the level of LAT fuel in said LATtank has dropped to below H_(LL).
 61. The method of claim 38, furtherincluding the step of selecting said OBS unit from one of a group ofseparation mechanisms consisting of silica gel, distillation, membranes,and polymer coated ceramic monoliths.
 62. The method of claim 38,further including for providing said OBS unit, the steps of: forming atubular porous inorganic ceramic substrate having a plurality ofchannels extending inward from one end; coating the channels with anassociated polymer; feeding said IAT fuel into said plurality ofchannels; taking said LAT fuel radially from said substrate; and takingsaid HAT fuel axially from said substrate.
 63. The method of claim 38,further including the step of cooling said LAT and said HAT fuels aftertaking them from said OBS unit.
 64. The method of claim 46, wherein saidinternal combustion engine consists of a spark ignition internalcombustion engine, whereby said method further includes the steps ofdesignating each of said IAT, LAT, and HAT fuels in terms of RON(Research Octane Number).
 65. The method of claim 64, wherein saidautoignition fuels map consists of a RON Map to determine the RON fuelrequirement from the sensed torque and engine speed.
 66. The method ofclaim 46, wherein said internal combustion engine consists of a dieseltype compression combustion ignition engine, whereby said method furtherincludes the steps of designating each of said IAT, LAT, and HAT fuel interms of cetane number.
 67. The method of claim 66, wherein saidautoignition fuels map consists of a Cetane Map to determine the cetanefuel requirement from the sensed torque and engine speed.
 68. In amotorized vehicle including a main fuel tank, an on-board separation(OBS) unit, a low autoignition temperature (LAT) fuel tank, and aninternal combustion engine, a method for selectively delivering fuelfrom one or a combination of said main tank, OBS unit, and LAT tank tosaid engine, comprising the steps of: filling said main tank with apredetermined amount of fuel having an intermediate autoignitiontemperature (IAT); controllably delivering fuel from said main tank tosaid OBS unit; operating said OBS unit to produce an LAT grade fuel, anda high autoignition temperature (HAT) fuel; delivering said LAT fuelfrom said OBS unit to said LAT tank; controllably delivering said HATfuel in a retentate stream directly from said OBS unit to said engine ina first mode of operation; controllably delivering LAT fuel from saidLAT tank to said engine in a second mode of operation; sensing the levelof LAT fuel in said LAT tank; controllably delivering LAT fuel from saidOBS unit to said main tank, in response to said level sensing step, attimes that said LAT tank is filled to a predetermined level with LATfuel; controllably recycling LAT fuel from said LAT tank to said OBSunit, in response to said level sensing step, at times that said LATtank is filled to a predetermined level; limiting the delivery of HATfuel in said retentate stream to said main tank; controllably deliveringIAT fuel from said main tank to said engine in a third mode ofoperation; and controlling the production of LAT and HAT fuels by saidOBS unit both in response to said level sensing step, and to match thedemand for these fuels by said engine at any given time.
 69. A vehiclemounted fuel management system for delivering individually and/or indifferent mixtures a plurality of different grades of fuel eachdesignated in terms of autoignition temperature to an associatedinternal combustion engine, comprising: a main tank for containing afuel having an intermediate autoignition temperature (IAT); an on-boardseparation (OBS) unit receptive of IAT fuel, said OBS unit beingoperable for separating said IAT fuel into at least a low autoignitiontemperature (LAT) fuel, and a high autoignition temperature (HAT) fuel,lower and higher than said IAT fuel, respectively; flow control meansfor feeding IAT fuel from said main tank to said OBS unit; an LAT tankfor receiving and containing LAT fuel from said OBS unit; means formeasuring the level of LAT fuel in said LAT tank; means for controllablyand selectively delivering either LAT fuel from said LAT tank, or HATfuel directly from said OBS unit, or a mixture thereof to said engine,in response to both said level measuring means, and the operationalrequirements of said engine at any given time; and means for controllingthe speed of said flow control means to obtain a feed rate of said IATfuel to said OBS unit, to control the latter's production of LAT and HATfuels to match the demand for these fuels by said engine at any giventime.
 70. The fuel management system of claim 69, wherein said OBS unitis selected from one of a group of separation mechanisms consisting ofsilica gel, distillation, membranes, and polymer coated ceramicmonoliths.
 71. The fuel management system of claim 69, wherein said OBSunit includes: a tubular porous inorganic ceramic substrate having aplurality of channels extending inward from one end; and an associatingpolymer coated on said channels, said channels being configured forreceiving IAT fuel from said pump, whereby LAT fuel can be takenradially from said substrate, and HAT fuel can be taken axially fromsaid substrate.
 72. The fuel management system of claim 69, furtherincluding: accumulator means connected between said main tank and a HAToutput port of said OBS unit, for providing a storage space or volumefor both storing excess HAT fuel produced by said OBS unit, andproviding a fluid pathway for fuel from said main tank to be deliveredto said engine in the even insufficient HAT and/or LAT fuels areavailable for delivery to said engine.
 73. The fuel management system ofclaim 72, wherein said accumulator means includes an accumulator havingan open storage volume.
 74. The fuel management system of claim 72,wherein said accumulator means includes a piston accumulator.
 75. Thefuel management system of claim 74, wherein said piston accumulatorincludes a two-way check valve for both permitting HAT fuel in saidstorage volume to be pushed out of said accumulator by movement of apiston in one direction, to help overcome a deficiency in HAT fuel at agiven time, and for permitting IAT fuel to be delivered to said enginewhen said piston moves opposite to said one direction to make up forinsufficient HAT fuel and/or LAT fuel.
 76. The fuel management system ofclaim 69, further including: means for selectively delivering either HATfuel to a direct fuel injector of said engine, or IAT fuel to saiddirect fuel injector in the event of an insufficiency of HAT fuel at anygiven time.
 77. The fuel management system of claim 76, furtherincluding means for delivering LAT fuel to a port fuel injector of saidengine.
 78. The fuel management system of claim 69, further includingmeans for delivering LAT fuel to a port fuel injector of said engine.79. The fuel management system of claim 69, further including: means forpreheating IAT fuel before its delivery to said OBS unit.